1,258 research outputs found
Influence of deflocculant on the isoelectric point of refractory powders: Considerations on the action of deflocculant
Isoelectric point changes in suspensions of refractory materials vis-a-vis the role of deflocculants used in monolithic refractories were investigated by considering the mineral compositions and adsorbed ions in four kinds of clay. Three types of curves represented the relation between the isoelectric point and the deflocculant. The surface charge of clay particles in the suspensions became negative as a result of the deflocculant, since the isoelectric point of suspensions decreased as the deflocculant was added. The isoelectric point changes of calcined alumina were also compared with those of the clays, and a similar phenomenon was observed, except that the deflocculant dispersed the calcined alumina better than it did the clays. A simple model was used to analyze the results
New DRIE-Patterned Electrets for Vibration Energy Harvesting
This paper is about a new manufacturing process aimed at developing stable
SiO2/Si3N4 patterned electrets using a Deep Reactive Ion Etching (DRIE) step
for an application in electret-based Vibration Energy Harvesters (e-VEH). This
process consists in forming continuous layers of SiO2/Si3N4 electrets in order
to limit surface conduction phenomena and is a new way to see the problem of
electret patterning. Experimental results prove that patterned electrets
charged by a positive corona discharge show excellent stability with high
surface charge densities that may reach 5mC/m^2 on 1.1\mu m-thick layers, even
with fine patterning and harsh temperature conditions (up to 250{\deg}C). This
paves the way to new e-VEH designs and manufacturing processes.Comment: Proc. European Energy Conference, 201
Temporal and sequential changes of glial cells and cytokine expression during neuronal degeneration after transient global ischemia in rats
<p>Abstract</p> <p>Background</p> <p>How glial cells and cytokines are associated with the progression of delayed neuronal death induced by transient global ischemia is still unclear. To further clarify this point, we studied morphological changes in glial cells (microglial cells and astrocytes), and cytokine protein levels, during the progression of neuronal cell loss in CA1 (Cornu Ammonis 1) of the hippocampus after transient global ischemia.</p> <p>Methods</p> <p>Morphological changes in glial cells were studied immuno-histochemically. Nine cytokines (IL-1Ī±, IL-1Ī², IL-2, IL-4, IL-6, IL-10, GM-CSF, IFN-Ī³ and TNF-Ī±) were simultaneously measured by a multiplexed bead-based immunoassay from 6 h to day21 after transient four vessel occlusion (4VO) in rats.</p> <p>Results</p> <p>During the process of neuronal loss, we observed four distinct phases: (1) lag phase day0-2 (no NeuN+ cell loss observed), (2) exponential phase day2-7 (NeuN+ cells reduced in number exponentially), (3) deceleration phase day7-14 (reduction rate of NeuN+ cells became low), (4) stationary phase day14 onward (NeuN+ cell loss progressed no longer). In the lag phase, activated glial cells were observed in the entire hippocampus but later were gradually restricted to CA1. Cytokine protein levels in the lag and exponential phases were lower than in the deceleration and stationary phases. IL-1Ī±, IL-1Ī², IL-4, IL-6 and IFN-Ī³ in 4VO were significantly higher in all four phases than in sham. Compared with sham level, GM-CSF was significantly high in the deceleration phase. TNF-Ī± was significantly high in both the deceleration and stationary phases.</p> <p>Conclusion</p> <p>Ischemic stress in 4VO activated glial cells in areas beyond CA1 in the lag phase. Pyramidal neurons were injured in CA1 from the end of the lag phase and then neuronal cells reduced in CA1 in the exponential phase. After neuronal death began, the influence of dead cells on glial cells and cytokine expression gradually became stronger than the influence by ischemic stress. Therefore, from the deceleration phase, changes in glial cells and cytokine production were likely caused by dead cells. Cytokine interaction in the microenvironment may determine the functions of IL-1Ī±, IL-1Ī², IL-4, IL-6 and IFN-Ī³ in all four phases. The function of GM-CSF and TNF-Ī± in the deceleration phase may be neurotrophic.</p
Membrane Potential and Bicarbonate Secretion in Isolated Interlobular Ducts from Guinea-pig Pancreas
The interlobular duct cells of the guinea-pig pancreas secrete HCO3ā across their luminal membrane into a HCO3ā-rich (125 mM) luminal fluid against a sixfold concentration gradient. Since HCO3ā transport cannot be achieved by luminal Clā/HCO3ā exchange under these conditions, we have investigated the possibility that it is mediated by an anion conductance. To determine whether the electrochemical potential gradient across the luminal membrane would favor HCO3ā efflux, we have measured the intracellular potential (Vm) in microperfused, interlobular duct segments under various physiological conditions. When the lumen was perfused with a 124 mM Clā-25 mM HCO3ā solution, a condition similar to the basal state, the resting potential was approximately ā60 mV. Stimulation with dbcAMP or secretin caused a transient hyperpolarization (ā¼5 mV) due to activation of electrogenic Na+-HCO3ā cotransport at the basolateral membrane. This was followed by depolarization to a steady-state value of approximately ā50 mV as a result of anion efflux across the luminal membrane. Raising the luminal HCO3ā concentration to 125 mM caused a hyperpolarization (ā¼10 mV) in both stimulated and unstimulated ducts. These results can be explained by a model in which the depolarizing effect of Clā efflux across the luminal membrane is minimized by the depletion of intracellular Clā and offset by the hyperpolarizing effects of Na+-HCO3ā cotransport at the basolateral membrane. The net effect is a luminally directed electrochemical potential gradient for HCO3ā that is sustained during maximal stimulation. Our calculations indicate that the electrodiffusive efflux of HCO3ā to the lumen via CFTR, driven by this gradient, would be sufficient to fully account for the observed secretory flux of HCO3ā
Mg/O<sub>2</sub> Battery Based on the Magnesium-Aluminum Chloride Complex (MACC) Electrolyte
Mg/O<sub>2</sub> cells employing
a MgCl<sub>2</sub>/AlCl<sub>3</sub>/DME (MACC/DME) electrolyte are
cycled and compared to cells with
modified Grignard electrolytes, showing that performance of magnesium/oxygen
batteries depends strongly on electrolyte composition. Discharge capacity
is far greater for MACC/DME-based cells, while rechargeability in
these systems is severely limited. The Mg/O<sub>2</sub>-MACC/DME discharge
product comprises a mixture of MgĀ(ClO<sub>4</sub>)<sub>2</sub> and
MgCl<sub>2</sub>, with the latter likely formed from slow decomposition
of the former. The presence of Cl in these compounds suggests that
the electrolyte participates in the cell reaction or reacts readily
with the initial electrochemical products. A rate study suggests that
O<sub>2</sub> diffusion in the electrolyte limits discharge capacities
at higher currents. Formation of an insulating product film on the
positive electrodes of Mg/O<sub>2</sub>-MACC/DME cells following deep
discharge increases cell impedance substantially and likely explains
the poor rechargeability. An additional impedance rise consistent
with film formation on the Mg negative electrode suggests the presence
of detrimental O<sub>2</sub> crossover. Minimizing O<sub>2</sub> crossover
and bypassing charge transfer through the discharge product would
improve battery performance
Repeated freezeāthaw cycles reduce the survival rate of osteocytes in bone-tendon constructs without affecting the mechanical properties of tendons
Frozen bone-patellar tendon bone allografts are useful in anterior cruciate ligament reconstruction as the freezing procedure kills tissue cells, thereby reducing immunogenicity of the grafts. However, a small portion of cells in human femoral heads treated by standard bone-bank freezing procedures survive, thus limiting the effectiveness of allografts. Here, we characterized the survival rates and mechanisms of cells isolated from rat bones and tendons that were subjected to freezeāthaw treatments, and evaluated the influence of these treatments on the mechanical properties of tendons. After a single freezeāthaw cycle, most cells isolated from frozen bone appeared morphologically as osteocytes and expressed both osteoblast- and osteocyte-related genes. Transmission electron microscopic observation of frozen cells using freeze-substitution revealed that a small number of osteocytes maintained large nuclei with intact double membranes, indicating that these osteocytes in bone matrix were resistant to ice crystal formation. We found that tendon cells were completely killed by a single freezeāthaw cycle, whereas bone cells exhibited a relatively high survival rate, although survival was significantly reduced after three freezeāthaw cycles. In patella tendons, the ultimate stress, Youngās modulus, and strain at failure showed no significant differences between untreated tendons and those subjected to five freezeāthaw cycles. In conclusion, we identified that cells surviving after freezeāthaw treatment of rat bones were predominantly osteocytes. We propose that repeated freezeāthaw cycles could be applied for processing bone-tendon constructs prior to grafting as the treatment did not affect the mechanical property of tendons and drastically reduced surviving osteocytes, thereby potentially decreasing allograft immunogenecity
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